How to used the mousescroll to as a modal function to, for example, move the object?
The event.type that you get within modal() will be WHEELUPMOUSE or WHEELDOWNMOUSE when the scrollwheel is used.

def modal(self, context, event):
    if event.type == 'WHEELUPMOUSE':
        context.object.location.x += 0.5
    elif event.type == 'WHEELDOWNMOUSE':
        context.object.location.x -= 0.5
    elif event.type == 'ESC':
        return {'CANCELLED'}

    return {'RUNNING_MODAL'}